JP2010263111A - Method of exciting superconducting electromagnetic apparatus and superconducting electromagnetic apparatus used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of exciting a superconducting electromagnetic apparatus capable of reducing the amount of penetration of heat into a cryostat, and to provide the superconducting electromagnetic apparatus. <P>SOLUTION: When adjusting a correction magnetic field by at least one specific superconducting shim coil, in a plurality of superconducting shim coils, a permanent current shim coil connected to the specific superconducting shim switch is turned on, while an excitation current flowing from an exciting power supply to a superconducting main coil is changed, thus an induction current is made to flow to the specific superconducting shim coil and the exciting current for flowing is made to flow, based on the induction current. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for exciting a superconducting electromagnet apparatus and a superconducting electromagnet apparatus used therefor.

  In general, in a superconducting electromagnet apparatus, a superconducting main coil that generates a magnetic field is installed in a cryostat for cooling. In order to improve the uniformity of the magnetic field generated by the superconducting main coil, a plurality of superconducting magnets are included in the same cryostat. A shim coil is installed. In the superconducting electromagnet apparatus disclosed in FIG. 8 of Patent Document 1, the superconducting main coil and the plurality of superconducting shim coils are each connected to an excitation power source disposed outside the cryostat through current leads. A permanent current main switch is connected in parallel to the superconducting main coil, and a permanent current shim switch is connected in parallel to each superconducting shim coil.

  In this conventional superconducting electromagnet apparatus, the permanent current main switch and each permanent current shim switch are set in a resistance state, that is, in an off state, and in a state where an exciting current is supplied from an exciting power source to the superconducting main coil and the superconducting shim coil, Both permanent current shim switches are both in a superconducting state, that is, in an on state. As a result, a permanent current flows through each of the permanent current circuits including the superconducting main coil and the permanent current main switch, and each superconducting shim coil and the corresponding permanent current shim switch. A shim coil generates a highly uniform magnetic field.

FIG. 8 of JP 2000-156316 A and its explanation

  In the conventional superconducting electromagnet apparatus shown in FIG. 8 of Patent Document 1, it is necessary to pass an exciting current from the exciting power supply to a current lead that connects each of the plurality of superconducting shim coils to the exciting power supply. These current leads connect a normal temperature portion outside the cryostat and a low temperature portion inside the cryostat, for example, a refrigerant temperature of 4.2 K, and in order to flow an excitation current through these, There is a problem that the amount of heat penetration increases.

  The present invention proposes an exciting method for a superconducting electromagnet apparatus and a superconducting electromagnet apparatus used therefor, which can improve this problem and reduce the amount of heat intrusion from a current lead to a plurality of superconducting shim coils.

  An exciting method of a superconducting electromagnet apparatus according to the present invention includes a superconducting main coil connected to an excitation power source, a plurality of superconducting shim coils that are magnetically coupled to the superconducting main coil and correct the magnetic field uniformity by the superconducting main coil, and a superconducting main coil A permanent current main switch connected in parallel to each other, a plurality of permanent current shim switches connected to each of the plurality of superconducting shim coils, and a superconducting main coil, a plurality of superconducting shim coils, a permanent current main switch, and a plurality of permanent current shim switches. An exciting method for a superconducting electromagnet apparatus having a cryostat to be accommodated, wherein an exciting current flowing from an exciting power source to the superconducting main coil when adjusting a correction magnetic field by at least one specific superconducting shim coil among a plurality of superconducting shim coils In a state of changing Of connected to the superconducting shim coils the permanent current shims switch is turned on, flowing an induced current to a particular superconducting shim coils, and wherein flowing the excitation current based on the induced current.

  A superconducting electromagnet apparatus according to the present invention includes a superconducting main coil connected to an excitation power source, a plurality of superconducting shim coils that are magnetically coupled to the superconducting main coil and correct the uniformity of the magnetic field by the superconducting main coil, and in parallel with the superconducting main coil. A cryostat housing a connected permanent current main switch, a plurality of permanent current shim switches connected to each of the plurality of superconducting shim coils, and a superconducting main coil, a plurality of superconducting shim coils, a permanent current main switch, and a plurality of permanent current shim switches A superconducting electromagnet apparatus comprising: a plurality of superconducting shim coils that are not connected to an excitation power source, and a superconducting main coil is used when adjusting a correction magnetic field by at least one specific superconducting shim coil among the plurality of superconducting shim coils The excitation current of In state, the permanent current shims switch connected to a particular superconducting shim coils is turned on, flowing an induced current to a particular superconducting shim coils, and wherein flowing the excitation current based on the induced current.

  The superconducting electromagnet apparatus according to the present invention includes a superconducting main coil connected to an excitation power source, a plurality of superconducting shim coils that are magnetically coupled to the superconducting main coil and correct the magnetic field uniformity by the superconducting main coil, and a superconducting main coil. Contains a permanent current main switch connected in parallel, a plurality of permanent current shim switches connected to each of a plurality of superconducting shim coils, and a superconducting main coil, a plurality of superconducting shim coils, a permanent current main switch, and a plurality of permanent current shim switches A superconducting electromagnet device having a cryostat that further includes an excitation power source, a permanent current main switch, and a control device that controls a plurality of permanent current shim switches in common, and at least one specific one of the plurality of superconducting shim coils Adjusting the correction magnetic field by the superconducting shim coil When the controller is in a state of changing the excitation current of the superconducting main coil, the control apparatus is characterized in that the on-state permanent current shims switch connected to a particular superconducting shim coils.

  In the exciting method and superconducting electromagnet apparatus according to the present invention, when adjusting the correction magnetic field by at least one specific superconducting shim coil among the plurality of superconducting shim coils, the excitation current of the superconducting main coil is changed. A permanent current shim switch connected to a specific superconducting shim coil is turned on, an induced current is passed through the specific superconducting shim coil, and an exciting current is caused to flow based on this induced current, so the current lead that connects the superconducting shim coil to the exciting power supply The exciting current can be prevented from flowing through this current lead, and therefore the amount of heat penetration from the current lead into the cryostat can be reduced.

FIG. 1 is an electric circuit diagram showing a superconducting electromagnet apparatus used in Embodiment 1 of a superconducting electromagnet apparatus excitation method according to the present invention. FIG. 2 is an operation explanatory diagram of the excitation method of the superconducting electromagnet apparatus according to the first embodiment. FIG. 3 is an electric circuit diagram showing the superconducting electromagnet apparatus used in Embodiment 2 of the exciting method of the superconducting electromagnet apparatus according to the present invention. FIG. 4 is an electric circuit diagram showing a superconducting electromagnet apparatus used in Embodiment 3 of the exciting method of the superconducting electromagnet apparatus according to the present invention.

  Several embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is an electric circuit diagram showing a superconducting electromagnet apparatus used in Embodiment 1 of the exciting method of the superconducting electromagnet apparatus according to the present invention. This superconducting electromagnet apparatus includes a superconducting main coil MC, a superconducting shim coil SC, a permanent current main switch MS, a permanent current shim switch SS, a flywheel circuit 17, a cryostat 30, and an excitation power source 40. Superconducting main coil MC, superconducting shim coil SC, permanent current main switch MS, permanent current shim switch SS, and flywheel circuit 17 are housed inside cryostat 30. Liquid helium is enclosed in the cryostat 30. The excitation power supply 40 is an excitation power supply for exciting only the superconducting main coil MC, and does not excite the superconducting shim coil SC, but is disposed outside the cryostat 30.

  The superconducting main coil MC is configured, for example, by connecting two superconducting main coils MC1 and MC2 in series. Superconducting shim coil SC includes a plurality of superconducting shim coils SC1, SC2,. These superconducting shim coils SC1, SC2,..., SCn are for correcting the uniformity of the magnetic field by the superconducting main coil MC, and are arranged at different positions coaxially with the superconducting main coil MC. Specifically, these superconducting shim coils SC1, SC2,..., SCn have the same inductance and are magnetically coupled to the superconducting main coil MC with the same polarity.

  The permanent current main switch MS is connected in parallel with the superconducting main coil MC. The permanent current main switch MS is constituted by, for example, a thermal permanent current switch, and includes a switch coil 11 and a heater 12 corresponding thereto. The permanent current main switch MS can take a superconducting state, that is, an on state, and a resistance state, that is, an off state. The heater 12 is connected to a heater power supply 14 through a control switch 13. The heater power supply 14 and the control switch 13 are disposed outside the cryostat 30. The switch coil 11 is in a superconducting state, that is, an on state when the control switch 13 is turned off, and is in a resistance state, that is, an off state when the control switch 13 is turned on and the heater 12 is heated. The permanent current main switch MS constitutes a permanent current circuit 15 for the superconducting main coil MC in the ON state. The permanent current circuit 15 is a circuit including the superconducting main coil MC and the switch coil 11.

  The flywheel circuit 17 is connected in parallel with the superconducting main coil MC. The flywheel circuit 17 includes a pair of flywheel diodes 171 and 172. The flywheel diodes 171 and 172 are connected in parallel with opposite polarities.

  The excitation power source 40 is connected to the superconducting main coil MC through a pair of current leads 41 and 42 to the superconducting main coil MC. The current leads 41 and 42 are disposed so as to penetrate the wall surface of the cryostat 30 and connect the superconducting main coil MC and the excitation power supply 40.

  The permanent current shim switch SS includes a plurality of permanent current shim switches SS1, SS2,. These permanent current shim switches SS1, SS2,..., SSn are connected to corresponding superconducting shim coils SC1, SC2,. These permanent current shim switches SS1, SS2,..., SSn are each constituted by, for example, a thermal permanent current switch, and include a switch coil 21 and a heater 22 corresponding thereto. These permanent current shim switches SS1, SS2,..., SSn can take a superconducting state, that is, an on state and a resistance state, that is, an off state, respectively. The heater 22 is connected to a heater power supply 24 through a control switch 23. The heater power supply 24 and the control switch 23 are disposed outside the cryostat 30. The switch coil 21 is in a superconducting state, that is, an on state when the control switch 23 is turned off, and is in a resistance state, that is, an off state when the control switch 23 is turned on and the heater 22 is heated. These permanent current shim switches SS1, SS2,..., SSn have their respective permanent current circuits 251, 252,..., 25n for the corresponding superconducting shim coils SC1, SC2,. Constitute. These permanent current circuits 251, 252,..., 25n are circuits including superconducting shim coils SC1, SC2,.

  FIG. 2 is an operation explanatory diagram of the excitation method of the superconducting electromagnet device according to the first embodiment. 2, (a) shows the exciting current of the superconducting main coil MC, (b) shows the heater current of the permanent current main switch MS, (c) shows the exciting current of the superconducting shim coil SC1, (d). Is the heater current of the permanent current shim switch SS1, (e) is the excitation current of the superconducting shim coil SC2, (f) is the heater current of the permanent current shim switch SS2, (g) is the excitation current of the superconducting shim coil SC3, ( h) shows the heater current of the permanent current shim switch SS3, respectively. The heater current in FIG. 2 (b) is the current flowing through the heater 12, and the heater currents in FIGS. 2 (d), (f), and (h) are applied to the heaters 22 corresponding to the superconducting shim coils SC1, SC2, and SC3, respectively. It is a flowing current. 2 (b), (d), (f), and (h), the high current level H and the low level L of each heater current, and the corresponding permanent current main switch MS and each of the permanent current shim switches SS1, SS2, and SS3 are shown. The off state (OFF) and the on state (ON) are displayed in parentheses.

  The horizontal axis in FIG. 2 is a time axis common to (a) to (h). Time points t0 to t14 are plotted along this time axis. Initial excitation A is shown between time t0 and time t2, magnetic field measurement B is shown between time t1 and time t2, magnetic field adjustment C is shown between time t4 and time t13, and steady operation D is shown after time t13. It is.

  FIG. 2 shows excitation currents of representative superconducting shim coils SC1, SC2, and SC3 in the superconducting shim coil SC in addition to the exciting current of the superconducting main coil MC, and the permanent current main switch MS and the permanent current corresponding thereto. The heater current of shim switch SS1, SS2, SS3 is shown. With reference to FIG. 2, an excitation method for the superconducting electromagnet apparatus of FIG. 1 will be described. In FIG. 2, the inside of the cryostat 30 is continuously maintained at a refrigerant temperature of, for example, 4.2K. At this temperature, the superconducting main coil MC and the superconducting shim coils SC1 to SCn are all in a superconducting state, and the permanent current main switch MS and the permanent current shim switches SC1 to SCn are in a superconducting state when their respective heater currents are turned off. That is, it is turned on.

First, initial excitation A is executed. At time t0, the excitation power supply 40 starts outputting. As shown in FIG. 2A, the exciting current flowing from the exciting power supply 40 to the superconducting main coil MC increases from the time point t0 to the time point t1, and this exciting current reaches the rated current value I _OP at the time point t1. . Between time t0 and t1, as shown in FIG. 2B, the permanent current main switch MS is turned off, and between time t0 and t1, FIGS. 2D, 2F and 2H. As shown in FIG. 2, the permanent current shim switches SS1, SS2, and SS3 are also turned off, and the excitation currents for the superconducting shim coils SC1, SC2, and SC3 become zero as shown in FIGS. 2 (c), (e), and (g). .

Between the time points t1 and t2, as shown in FIG. 2B, the permanent current main switch MS is turned on, and the permanent current shim switches SS1, SS2, and SS3 are turned off. Magnetic field measurement B is executed between time points t1 and t2. This magnetic field measurement B is performed in a state where the permanent current main switch MS is turned on and the exciting current of the superconducting main coil MC is held at the rated current value _IOP . In this magnetic field measurement B, the uniformity of the magnetic field by the superconducting main coil MC is measured, and the excitation current value for each of the superconducting shim coils SC1 to SCn is determined in order to correct the uniformity. In addition, between times t2-t3, the persistent current main switch MS and persistent current shim switch SS1~SSn are both set OFF state, the exciting current flowing through the superconducting main coil MC is returned to zero from the rated current I _OP. Between time points t3 and t4, the exciting currents of the superconducting main coil MC and the superconducting shim coils SC1 to SCn become zero, and the permanent current main switch MS and the permanent current shim switches SS1 to SSn are all turned on.

The magnetic field generated by the superconducting main coil MC is distorted in the uniformity of the magnetic field at the center of the superconducting electromagnet device due to manufacturing errors and the like. This magnetic field needs to be uniformized to a high uniformity of 2 ppm or less in a space of, for example, a 500 mm sphere, and in order to obtain this high uniform magnetic field, the excitation current values for the respective superconducting shim coils SC1 to SCn are determined. The exciting current value for each superconducting shim coil SC1 to SCn is determined independently for each superconducting shim coil SC1 to SCn. The excitation current value for each of the superconducting shim coils SC1 to SCn is generally a mixture of a first polarity, for example, a negative polarity excitation current value and a second polarity, for example, a positive polarity excitation current value. In some cases, only the excitation current value of one polarity is used, or in the case of only the excitation current value of the second polarity. There may also be a superconducting shim coil whose excitation current value is zero. Figure 2 is the steady operation D, the excitation current of the superconducting shim coils SC1 shown in (c) is the excitation current value -i ₁ of the first polarity, excitation current first superconducting shim coils SC2 shown in the (e) An example is shown in which the excitation current value of the polarity is −i ₂ and the excitation current of the superconducting shim coil SC3 shown in (g) is the excitation current value of the second polarity + i ₃ .

Magnetic field adjustment C is performed between time points t4 and t13. In the magnetic field adjustment C, and the final stage, with respect to the superconducting main coil MC, passing a magnetizing current of the rated current I _OP, also for each of the superconducting shim coils SC1 through SCn, as a result of magnetic field measurement B Magnetic field adjustment is performed so that the determined excitation current value flows. In the example of FIG. 2, in the final stage of the magnetic field adjusting C, the exciting current of the superconducting shim coils SC1 shown in FIG. 2 (c) is the excitation current value -i _1, the exciting current of the superconducting shim coils SC2 shown in FIG. 2 (e) There is an exciting current -i _2, also, the exciting current of the superconducting shim coils SC3 shown in FIG. 2 (g) is the excitation current + _{i 3.}

Regarding the magnetic field adjustment C, adjustment of excitation currents of the superconducting shim coils SC1, SS2, and SS3 will be specifically described. First, between the time points t4 and t5, the permanent current main switch MS and the permanent current shim switches SS1, SS2, and SS3 are all turned off, and the excitation current flowing from the excitation power supply 40 to the superconducting main coil MC is increased again. At time t5, the exciting current of the superconducting main coil MC becomes an exciting current value of (I _OP −I ₁ ), and this exciting current value is held until time t6. -I ₁ corresponds to the excitation current value -i ₁ in steady operation D of the superconducting shim coils SC1. The permanent current main switch MS and the permanent current shim switches SS1, SS2, and SS3 maintain the OFF state between the time points t5 and t6, but just before the time point t6, only the heater current of the permanent current shim switch SS1 is at the low level L. The permanent current shim switch SS1 is maintained in the ON state including the steady operation D thereafter.

Between time points t6 and t7, the excitation current of the superconducting main coil MC is increased again, and at time point t7, the excitation current becomes an excitation current value of (I _OP −I ₂ ), and this excitation current value becomes the time point t8. Hold up. −I ₂ corresponds to the exciting current value −i ₂ in the steady operation D of the superconducting shim coil SC2. Between time points t6 and t7, the permanent current shim switch SS1 is maintained in the ON state, and in this state, the exciting current of the superconducting main coil MC is from (I _OP −I ₁ ) to (I _OP −I ₂ ). Increase. Thus, between times t6-t7, the excitation current of the superconducting main coil MC _is based on the fact that changes from _(I OP -I ₁₎ to _(I OP -I _2), induction current flows through the superconducting shim coils SC1 . This induced current has a magnitude corresponding to a change in excitation current of the superconducting main coil MC + I ₁₂ = (I _OP −I ₂ ) − (I _OP −I ₁ ) = I ₁ −I ₂ . Since the polarity is positive, the excitation current is the first polarity, that is, negative polarity. As a result, the excitation current of the superconducting shim coil SC1 becomes −i ₁₂ = − (i ₁ −i ₂ ) = − i ₁ + i ₂ corresponding to + I ₁₂ at time t7 as shown in FIG. The exciting current value −i ₁₂ is maintained until time t8.

Between the time points t7 and t8, the permanent current shim switch SC1 is maintained in the on state, and the permanent current main switch MS and the permanent current shim switches SS2 and SS3 are maintained in the off state. The heater current of the shim switch SS2 changes to the low level L, and the permanent current shim switch SS2 thereafter maintains the ON state including the steady operation D. Between the time points t8 and t9, the permanent current shim switches SS1 and SS2 are kept on, the permanent current main switch MS and the permanent current shim switch SS3 are turned off, and the excitation flowing from the excitation power source 40 to the superconducting main coil MC. Increase the current again. At time t9, the excitation current of the superconducting main coil MC reaches the rated current value _{I OP,} the rated current value _{I OP} is held until the time t10.

Between the time points t8 and t9, the permanent current shim switches SS1 and SS2 are maintained in the on state, and in this state, the exciting current of the superconducting main coil MC is from (I _OP −I ₂ ) to the rated current value I _OP. Increase. Therefore, between time points t8 and t9, based on the fact that the exciting current of the superconducting main coil MC changes from (I _OP −I ₂ ) to the rated current value I _OP , induced currents are induced in the superconducting shim coil SC1 and the superconducting shim coil SC2. Flows. This induced current has a magnitude corresponding to the change in excitation current of the superconducting main coil MC + I ₂ , and since the change has a positive polarity, it becomes a first polarity, that is, a negative polarity excitation current. As a result, the exciting current of the superconducting shim coil SC1 reaches the exciting current value (−i ₁₂ −i ₂ ) = − i ₁ corresponding to (+ I ₁₂ + I ₂ ) at time t9 as shown in FIG. The excitation current value -i ₁ is maintained until time t10. As shown in FIG. 2 (e), the exciting current of the superconducting shim coil SS2 decreases to −i ₂ corresponding to + I ₂ at time t9, and this exciting current value −i ₂ is maintained until time t10.

In between times t10-t11, the excitation current of the superconducting main coil MC is increased by + _{I 3} from the rated current _{I OP.} + I ₃ corresponds to the exciting current i ₃ in the steady operation D of the superconducting shim coil SC3. This Between times t10-t11, the persistent current shim switches SS1, SS2 has kept on, the excitation current of the superconducting main coil MC in this state is increased by + _{I 3} from the rated current _{I OP.} Therefore, between time points t10 and t11, based on the fact that the exciting current of the superconducting main coil MC changes from the rated current value I _OP to (I _OP + I ₃ ), an induced current is generated in the superconducting shim coil SC1 and the superconducting shim coil SC2. Flowing. This induced current has a magnitude corresponding to the change + I ₃ in the excitation current of the superconducting main coil MC. Since the polarity of the change is positive, it becomes the first polarity, that is, the negative polarity induced current. As a result, the excitation current of the superconducting shim coil SC1 decreases to an excitation current value (−i ₁ −i ₃ ) corresponding to (+ I ₁₂ + I ₂ + I ₃ ) at time t11 as shown in FIG. 2 (c). The excitation current value (−i ₁ −i ₃ ) is maintained until time t12. As shown in FIG. 2E, the exciting current of the superconducting shim coil SS2 decreases to (−i ₂ −i ₃ ) corresponding to (+ I ₂ + I ₃ ) at time t11, and this exciting current value (−i ₂ -i ₃ ) is maintained until time t12.

  Between the time points t11 and t12, the permanent current shim switches SS1 and SS2 are maintained in the on state, and the permanent current main switch MS and the permanent current shim switch SS3 are maintained in the off state. The heater current of the shim switch SS3 changes to the low level L, and the permanent current shim switch SS3 thereafter maintains the ON state including the steady operation D.

Between time t12 and t13, the exciting current of the superconducting main coil MC is reduced from (I _OP + I ₃ ) to the rated current value I _OP . + I ₃ corresponds to the exciting current i3 in the steady operation D of the superconducting shim coil SC3. During this time t12-t13, the permanent current shim switches SS1, SS2, SS3 are maintained in the ON state, and in this state, the exciting current of the superconducting main coil MC decreases from (I _OP + I ₃ ) to I _OP . . Therefore, between time t12 and t13, the superconducting shim coil SC1, superconducting shim coil SC2, and superconducting shim coil SC3 are based on the fact that the exciting current of the superconducting main coil MC changes from (I _OP + I ₃ ) to the rated current value I _OP. Inductive current flows through. This induced current has a magnitude corresponding to the change amount −I ₃ of the excitation current of the superconducting main coil MC, and the polarity of the change amount is negative. Therefore, the induced current is a second polarity, that is, a positive polarity induced current. As a result, the exciting current of the superconducting shim coil SC1 is, as shown in FIG. 2C, the exciting current value (−i ₁ −i ₃ + i) corresponding to (+ I ₁₂ + I ₂ + I ₃ −I ₃ ) at time t13. ₃₎ = - until _{i 1} increases, the excitation current value -i ₁ is maintained at time t13 subsequent steady operation D. The excitation current of the superconducting shim coil SS2 increases to (−i ₂ −i ₃ + i ₃ ) = − i ₂ corresponding to (+ I ₂ + I ₃ −I ₃ ) at time t13 as shown in FIG. The exciting current value -i ₂ is maintained in the steady operation D after time t13. Exciting current of the superconducting shim coils SS3, as shown in FIG. 2 (g), at time t13, and increases to the exciting current value + _{i 3} corresponding to -I _3, the excitation current value + _{i 3} is the time t13 after the steady operation D Maintained at.

In magnetic field adjustment C of FIG. 2, a superconducting main coil MC is the excitation current of the last time point t13 is the rated current _{I OP,} superconducting shim coils SS1, SS2, SS3, the exciting current of the phase of the last time point t13, respectively superconducting Excitation current values -i ₁ , -i ₂ , + i ₃ determined to correct the magnetic field generated by the main coil MC are used. In addition, the excitation currents at the final time point t13 are also applied to the other superconducting shim coils SS4 to SSn. The exciting current value determined to correct the magnetic field generated by the superconducting main coil MC is maintained.

  The steady operation D is executed after time t13. Immediately before time t14, the permanent current main switch MS is turned on, and the exciting current of the superconducting main coil MC is thereafter maintained at the rated current value IOP. At time t14, as indicated by a dotted line in FIG. 2A, the exciting current from the exciting power source 40 is cut off. In this steady operation D, the superconducting shim coils SS1, SS2, and SS3 are representative, and the other superconducting shim coils SS4 to SSn also maintain the determined excitation currents respectively. Therefore, the uniformity of the magnetic field combined with the superconducting main coil MC is high. Uniformity is maintained.

Thus induction, the magnetic field adjustment C of FIG. 2, the excitation current of the superconducting shim coils SC1 shown in FIG. 2 (c), corresponding to the change in + I ₁₂ of the excitation current of the superconducting main coil MC between time t6-t7 Current −i ₁₂ , induced current −i ₂ corresponding to the change in excitation current of superconducting main coil MC between time points t 8 and t 9 + I _2, and change in excitation current of superconducting main coil MC between time points t 10 and t 11. Algebraic sum −i ₁₂ −i ₂ −i of the induced current −i ₃ corresponding to + I ₃ and the induced current + i ₃ corresponding to the change −I ₃ in the excitation current of the superconducting main coil MC between time points t 12 and t _{13. 3 + i 3 = -i 1 +} i 2 -i 2 -i 3 + i 3 = a -i _1. Exciting current of the superconducting shim coils SC2 shown in FIG. 2 (e) and the induced current -i ₂ corresponding to the variation + _{I 2} of the excitation current of the superconducting main coil MC between time t8-t9, superconducting between time t10-t11 Algebra of induced current −i ₃ corresponding to change in excitation current of main coil MC + I ₃ and induced current + i ₃ corresponding to change in excitation current of superconducting main coil MC between time points t 12 and t 13 −I ₃ The sum −i ₂ −i ₃ + i ₃ = −i ₂ . The exciting current of the superconducting shim coils SC3 shown in FIG. 2 (g) is a induced current + _{i 3} corresponding to variation -I ₃ of the excitation current of the superconducting main coil MC between the time t12-t13.

  Thus, the exciting current of each superconducting shim coil SC1 to SCn is given as an induced current corresponding to the change in the exciting current of superconducting main coil MC. As a result, in the excitation method of the superconducting electromagnet apparatus according to the first embodiment, it is not necessary to supply an excitation current from the outside to each of the superconducting shim coils SC1 to SCn. The amount of heat intruding into the cryostat 30 can be eliminated. Further, in the first embodiment of the superconducting electromagnet apparatus shown in FIG. 1, it is not necessary to connect each of the superconducting shim coils SC1 to SCn to the shim coil exciting power source, and this shim coil exciting power source and this superconducting shim coil SC1 to SCn. It is possible to omit the current lead to be connected to, and it is possible to eliminate the amount of heat penetration that enters the cryostat 30 from the outside via this current lead. For example, when the maximum current of the superconducting shim coils SC1 to SCn is 50A and the number thereof is eight, the total current amount to the superconducting shim coils SC1 to SCn is 800A, which is about 2W thermal load. It becomes possible to reduce.

Embodiment 2. FIG.
FIG. 3 is an electric circuit diagram showing the superconducting electromagnet apparatus used in Embodiment 2 of the exciting method of the superconducting electromagnet apparatus according to the present invention. The superconducting electromagnet apparatus shown in FIG. 3 is obtained by adding shim coil excitation power sources 501 to 50n to the superconducting shim coils SC1 to SCn in addition to the superconducting electromagnet apparatus shown in FIG. These shim coil excitation power sources 501 to 50n are connected to the corresponding superconducting shim coils SC1 to SCn through a pair of current leads 5011, 5012 to 50n1, and 50n2 that respectively penetrate the wall surface of the cryostat 30. The other configuration is the same as in FIG.

  In the excitation method of the superconducting electromagnet apparatus according to the second embodiment, the initial excitation A, magnetic field measurement B, magnetic field adjustment C, and steady operation D are the methods shown in FIG. 2 without using the shim coil excitation power sources 501 to 50n. Is implemented in the same way. The shim coil excitation power sources 501 to 50n are used for recovering the accumulated energy of the superconducting shim coils SC1 to SCn when an emergency occurs in the steady operation D and the superconducting electromagnet apparatus is urgently demagnetized. In this emergency demagnetization, all of the permanent current main switch MS and the permanent current shim switches SS1 to SSn are simultaneously turned off, the magnetic field is demagnetized, and the energy stored in the superconducting main coil MC is supplied to the excitation power source 40 and the superconducting power. The stored energy of the shim coils SC1 to SCn is recovered by the shim coil excitation power sources 501 to 50n.

  In the exciting method of the superconducting electromagnet apparatus and the superconducting electromagnet apparatus according to Embodiment 2, the shim coil exciting power sources 501 to 50n and the current leads 5011, 5012 to 50n1, and 50n2 that connect them to the superconducting shim coils SC1 to SCn are eliminated. Although not possible, current leads 5011, 5012 to 50n1 from the excitation power sources 501 to 50n for the respective shim coils to the respective superconducting shim coils SC1 to SCn through the initial operation A, the magnetic field measurement B, the magnetic field adjustment C, and the steady operation D until the emergency demagnetization. , 50n2 can be prevented from flowing an exciting current, and therefore, the amount of heat penetration that the heat generated by these current leads 5011, 5012 to 50n1, and 50n2 enters the cryostat 30 can be reduced.

Embodiment 3 FIG.
FIG. 4 is an electric circuit diagram showing a superconducting electromagnet apparatus used in Embodiment 3 of the exciting method of the superconducting electromagnet apparatus according to the present invention. The superconducting electromagnet apparatus shown in FIG. 4 is obtained by adding a control device 60 to the superconducting electromagnet apparatus shown in FIG. Others are the same as the superconducting electromagnet apparatus shown in FIG.

  The control device 60 generates a control signal S40 for the excitation power source 40, a control signal S13 for the control switch 13, and control signals S231 to S23n for the control switches 23 in common. The control signal S40 controls the exciting current of the superconducting main coil MC as shown in FIG. 2 (a), and the control signal S13 is related to the control signal S40 as shown in FIG. 2 (b). The control signal S241 to S24n controls the permanent current shim switches SS1 to SSn as shown in FIGS. 2D, 2F and 2H in association with the control signal S40.

  The excitation method shown in FIG. 2 is based on the premise that the excitation power supply 40 and the control switches 13 and 23 are manually operated. In the superconducting electromagnet apparatus shown in FIG. The excitation method can be executed automatically.

  The present invention is utilized as a superconducting electromagnet apparatus used in, for example, a medical magnetic resonance imaging apparatus and the excitation method thereof.

MC: Superconducting main coil, SC1-SCn: Superconducting shim coil,
MS: permanent current main switch, SS1 to SSn: permanent current shim switch,
40: excitation power source, 60: control device.

Claims (5)

A superconducting main coil connected to an excitation power source, a plurality of superconducting shim coils that are magnetically coupled to the superconducting main coil to correct the uniformity of the magnetic field by the superconducting main coil, and a permanent current main connected in parallel to the superconducting main coil A switch, a plurality of permanent current shim switches connected to each of the plurality of superconducting shim coils, and a cryostat accommodating the superconducting main coil, the plurality of superconducting shim coils, the permanent current main switch, and the plurality of permanent current shim switches. An excitation method for a superconducting electromagnet apparatus comprising:
When the correction magnetic field by at least one specific superconducting shim coil among the plurality of superconducting shim coils is adjusted, the excitation current flowing from the excitation power source to the superconducting main coil is changed and connected to the specific superconducting shim coil. An excitation method for a superconducting electromagnet apparatus, wherein the permanent current shim switch is turned on, an induced current is caused to flow through the specific superconducting shim coil, and an exciting current is caused to flow based on the induced current.   2. The method of exciting a superconducting electromagnet device according to claim 1, wherein when the correction magnetic field by the specific superconducting shim coil is adjusted, the specific current is increased in the state of increasing the excitation current flowing from the excitation power source to the superconducting main coil. A superconducting electromagnet apparatus characterized in that the permanent current shim switch connected to a superconducting shim coil is turned on, an induced current having a first polarity is caused to flow through the specific superconducting shim coil, and an exciting current is caused to flow based on the induced current. Excitation method.   2. The method of exciting a superconducting electromagnet device according to claim 1, wherein when adjusting the correction magnetic field by the specific superconducting shim coil, the superconducting magnet coil is connected to the specific superconducting shim coil in a state in which the exciting current of the superconducting main coil is reduced. An excitation method for a superconducting electromagnet apparatus, wherein the permanent current shim switch is turned on, an induced current having a second polarity is passed through the specific superconducting shim coil, and an exciting current is caused to flow based on the induced current. A superconducting main coil connected to an excitation power source, a plurality of superconducting shim coils that are magnetically coupled to the superconducting main coil to correct the uniformity of the magnetic field by the superconducting main coil, and a permanent current main connected in parallel to the superconducting main coil A switch, a plurality of permanent current shim switches connected to each of the plurality of superconducting shim coils, and a cryostat accommodating the superconducting main coil, the plurality of superconducting shim coils, the permanent current main switch, and the plurality of permanent current shim switches. A superconducting electromagnet apparatus comprising:
The plurality of superconducting shim coils are not connected to an excitation power source, and the adjustment current of the superconducting main coil is changed when adjusting the correction magnetic field by at least one specific superconducting shim coil among the plurality of superconducting shim coils. A superconducting electromagnet apparatus, wherein the permanent current shim switch connected to the specific superconducting shim coil is turned on, an induced current is supplied to the specific superconducting shim coil, and an exciting current is supplied based on the induced current. . A superconducting main coil connected to an excitation power source, a plurality of superconducting shim coils that are magnetically coupled to the superconducting main coil to correct the uniformity of the magnetic field by the superconducting main coil, and a permanent current main connected in parallel to the superconducting main coil A switch, a plurality of permanent current shim switches connected to each of the plurality of superconducting shim coils, and a cryostat that accommodates the superconducting main coil, the plurality of superconducting shim coils, the permanent current main switch, and the plurality of permanent current shim switches. A superconducting electromagnet apparatus, further comprising a control device for commonly controlling the excitation power source, the permanent current main switch, and the plurality of permanent current shim switches;
When adjusting the correction magnetic field by the specific superconducting shim coil, the control unit changes the excitation current of the superconducting main coil, and the control unit changes the permanent current shim switch connected to the specific superconducting shim coil. A superconducting electromagnet apparatus characterized by being turned on.

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